This application claims the priority of German patent document 100 54 842.3, filed Nov. 4, 2000, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for electrically starting up a fuel cell in a fuel cell installation.
It is generally known from the state of the art that starting up a fuel cell in a fuel cell installation electrically may take place (in order to avoid damaging the fuel cell, especially the membranes of a PEM fuel cell) only when there is a sufficiently large flow of the hydrogen-containing gas originating from a gas-generating system and with a sufficiently high concentration of hydrogen in the fuel cell.
Therefore, in a very simple solution of this problem, a certain period of time is allowed to elapse after the start of the gas-generating system, before the fuel cell started up electrically. In this case, empirical values are used, which imply that after the elapsed time, it is a very likely that a flow of gas of adequate quality and amount is present in the region of the anode space of the fuel cell.
In order to optimize the starting-up process of such a fuel cell installation and to determine the presence of an adequate amount and an adequate quality of hydrogen-containing gas, Japanese publication JP 630 45 766 A1 discloses a temperature detector that is disposed in the region of a reformer of the gas-generating system. Once the reformer of the gas-generating system has reached a specified temperature, it is assumed that the reformer is operating correctly and that the appropriate amount of hydrogen-containing gas can be made available in the gas-generating system. A similar procedure is also disclosed in Japanese publication JP 021 58 061 A1.
It is a common feature of the two Japanese publications that the fuel cell or the anode space of the fuel cell has a bypass line, so that the gas originating from the gas-generating system is passed through the fuel cell only where the electrical switching-on of the fuel cell is imminent.
The two Japanese publications have the serious disadvantage that the condition of the gas-generating system can be determined only from the temperature in the region of the gas-generating system, from which corresponding conclusions concerning the correct working capability of the gas-generating system are then drawn. However, it is particularly disadvantageous that the quality and the amount of the hydrogen in the reformate itself cannot be determined.
It is therefore an object of the present invention to provide a method for the electrical starting up of a fuel cell in a fuel cell installation with a gas-generating system, which ensures that when the fuel cell is started up, a sufficient amount of hydrogen-containing gas with a sufficient concentration of hydrogen is available to operate the fuel cell.
Pursuant to the present invention, preferred embodiments of the present invention include combining a hydrogen-containing gas flow from a gas-generating system and an oxygen-containing gas flow downstream of a fuel cell; combusting the combined gas flows; and starting up the fuel cell electrically as a function of a temperature existing in a region of the combined gas flows.
The special advantage lies in the comparatively simple construction, which only requires that a temperature sensor be present in the region of combustion of the two gas flows downstream from the fuel cell.
A further decisive advantage is that the combustion takes place only downstream from the fuel cell, so that it can be ensured, by the course of the temperature, that the appropriate amount and quality of hydrogen-containing gas is supplied to the fuel cell. It is not assumed, as it is in the state of the art, that such a gas would, in all probability, have to be produced in the gas-generating system.
The space-saving method, using simple and robust components, has the advantage of a very high operational reliability and ensures a correspondingly long service life, without requiring a complex system of surfaces sensors.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the present invention when considered in conjunction with the accompanying drawings.